Date my be stamped on the bottom, or located on the bottom corner of one of the stickers front or rear. All dry chem's are recharged after 6 years. The powder has to be run through a screen to remove any lumpy powder. (I call them strawberries in a milkshake) If one of those lumps gets sucked onto the end of the pick up tube...no more powder. 12 years is the hydro interval. If yours have plastic valve bodies/nozzles they probably are non-rechargable and the Kidde is saying their life is 12 years...you have to remember there are no rules for residential or own use applications. You aren't even required to have a portable in your home let alone keep it in working order. I have helped from a dock in trying to put out a boat fire...not easy to do when gas is involved. A cheap portable may be better than nothing around the house...because you can always through it at the fire if it doesn't work and walk out the door....not so easy to do alone and 10 miles offshore. I would have good equipment on the boat and the minimum required is BS...like I said gas is not easy to put out especially if it is under pressure from a EFI system. You only get about 7 or 8 seconds of powder from those 2 1/2 pounders and about 15 seconds from a 5 pounder.